I've visually checked the motor mounts and they appear to be in excellent shape, easily over the 12mm gap you suggested. The only indications of driveshaft problems are the vibration around 80mph and the gearshift from 1st to 2nd is a little jerky. Most other conditions the car is very smooth. I am going to replace the flex disks and center bearing to see if that cures the problem. It looks a fairly straightforward job to do myself. I'm now pretty sure this is the cause of my problem, I'll let you know what happens. Again many thanks for all your help.
Colin

Just because they aligned it does not mean that there were not worn components.

Check the idler arm bushings. I had very similar symptoms when mine were worn.

Check the suspension balljoints for play, but you must unload them to detect.
Support control arm with jackstand, then check for play.

I'd spend a little more time trying to find the problem instead of throwing parts at it!

Sounds like paying an experienced mb mechanic an hour to inspect the car head to toe on a lift might be a cheap way to find the problem. Assuming you really want to do the repairs yourself.

I'd make sure all the front end parts are in good condition.

The toe out condition you described indicates the shop did not use the spreaderbar when aligning the car. It is to create road forces which spread the front tires outward at highway speed-then you set the toe.

Has this car always vibrated this way? Is this post tires? post struts??

M

Colin,
Since you are bent on pulling the driveline anyway, do yourself a favor and rotate the u joint while the front section of shaft is removed. There should be no catches in it except maybe at the centered position. If you feel any sort of catch anywhere off center. the driveline needs to be rebuilt. MB went to staked in joints like everone else. You'll have to send it to a rebuilder. Don't even try to do it yourself. The service I use is excellent and fairly priced. They include boxing and shipping in their price.
Power Train Ind. (800) 798-4585

I still think you might have a wheel balance problem or possibly an expanding belt on one of the tires. Swap front to back. I can't diagnose much closer considering the car I'm trying to diagnose is 3000 miles away.

Seems to me that some logic needs to be applied here. Before throwing parts at the problem.

1) Did the car display this vibration between 80 and 85 before the alignment and on the old tires? Yes or No.

2) Did the vibration occur after the alignment and before the new tires? Yes or No?

3) Did the vibration occur immediately after installing the new tires?

4) Did the vibration start to occur as the new tires gathered miles and
began to wear on the inside due to incorrect alignment?

5) The suggestion to move the rears to the front is a good way to diagnose the effect of wear. The rears shouldn't have worn on the inside. This would also eliminate the possibility that you have one bad tire in the front.

I have checked the front suspension and cannot find any signs of real wear. Everything seems to be in good shape. The car ran very smoothly for about 5000 miles before the vibration came back and I first noticed the wear on the inside of the tires. I will be getting the tires rotated and balanced this week at Sears (it's free with new tire purchase) and ask them to check the alignment again. I've had all my other cars aligned there before with no problems. Are Mercedes particularly sensitive regarding wheel alignment?
Also, after all your great advice, I agree the main problem is vibration from the driveshaft, so I will replace the bearing and flex disks, the front one looks like it's worn out and I like to replace parts like this as a matter of course.
I agree it may be best to take my car to a professional mechanic for at least troubleshooting the problem, but I have always worked on my own cars and see no need to pay someone when I can do the work myself, even a Mercedes, which for the most part has been a real pleasure to wrench on.
Thanks again everybody for your help. I'll keep you posted on developments. Stay tuned!
Colin

Is thre any damper on your steering?

Yes, I recently replaced the steering damper.
Colin

You could have had a professional diagnose the problem in about an hour. You've spent way more than you need to on parts, but hey if you're having fun. You are definitely different than most of the DIYs on this forum. Most don't want to spend the money on a single part until they are absolutely positively sure it will cure the problem.:)

I haven't bought any new parts yet. I've only replaced parts recently that were obviously worn out like the tires,struts and steering damper. I drive about 1000 miles a week and I need to keep the Merc reliable especially now it has over 207,000 miles on it.
I will definitely replace the flex disks etc. as the front one looks worn out.
For all the parts cost I think it is good preventative maintenance.
I will let you all know if that cures the problem. If not I promise I will take it to the dealer in Macon to let them check the car and at least do the wheel alignment again if thy deem that necessary.
Watch this space!
Colin :cool:

Find a tech who is accustomed to driving a car to check for vibrations. A tech will immediately be able to tell you whether the vibration is at wheel speed or driveshaft speed.

If it is at driveshaft speed, check the flex disks. If they are okay, put a washer between the carrier bearing mount and the body and retighten. Then see if the vibration is still there.

Good luck,

Is this a trick to put the needle bearings in the u joint at a different angle?

Absolutely sure the alignment is not correct from Sears.

Like I said- he may have the same hunter machine, but he won't own the spreader bar. The mercedes front suspension has rubber bushings.
If the guy has done a bunch of benz's correctly, he could get probably get it close without a spreader bar.

Agree with Larrybible. Take it to a mb tech and get them to drive the car and pay them to put it on a lift. They can pull and prod inspecting all the common things in about 15 minutes.


Michael

Yes, the washer will often get the u-joint away from the "notch" that is worn into it. I have seen this work more than once.

Have a great day,

It defenetly has something to do with the tires. When i changed the wheels on my SD to the 8 spoke 16in. wheels off a 93 s-class immedietly i had vibration at 50+mph. And i went to get new goodyear tires and get the car aligned it fixed the problem.